Recycling critical raw materials from waste electronic equipment
Recycling critical raw materials from waste electronic equipment
Recycling critical raw materials from waste electronic equipment
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<strong>Recycling</strong> <strong>critical</strong> <strong>raw</strong> <strong>materials</strong><br />
<strong>from</strong> <strong>waste</strong> <strong>electronic</strong> <strong>equipment</strong><br />
2.2 Rare earths<br />
Rare earths (also known as rare earth metals) are used in the luminescent material in visual<br />
display units. Depending on the display technology, the rare earths are either used in the<br />
displays themselves (PDP and OLED technology) or the background illumination (LCD<br />
technology). The available data on the use of rare earths in this context is of a very general<br />
nature, as all information on the quantities and concentrations for specific products is usually<br />
covered by trade secrets. The following statements can nevertheless be made:<br />
� For luminescent material a distinction can be made between the support matrix and<br />
the actual luminescent substances (activators). In addition to compounds without rare<br />
earths, compounds with yttrium (Y2O3), cerium (CeMgAl11O19) and lanthanum (La2O3)<br />
are used in the support matrix (Schüler et al. 2011). Data <strong>from</strong> the US Department of<br />
Energy (US DoE 2010), Guarde et al. (2010) and Gambardella et al. (2010) show that<br />
these three metals exhibit the largest proportions of all rare earths in luminescent<br />
<strong>materials</strong>. Gambarella et al. (2010) specify the proportion of yttrium, lanthanum and<br />
cerium in all rare earths used in luminescent <strong>materials</strong> as 69.2%, 11.0% and 8.5%,<br />
followed by europium (4.9%), terbium (4.6%) and gadolinium (1.8%).<br />
� Europium, terbium and gadolinium are used in different compounds for the actual<br />
luminescent substances. Samarium, erbium, dysprosium, thulium and lutetium play a<br />
quantitatively more minor role (Schüler et al. 2011; Gambardella et al. 2010).<br />
� According to Rieger (2009) the following rare earth compounds are used in plasma<br />
displays:<br />
Red: (Y, Gd)BO3:Eu<br />
(Y2O3:Eu 3+ )<br />
Green: (Y, Gd)BO3:Tb<br />
Blue: BaMgAl10O17:Eu<br />
� Cold cathode tubes (CCFL) are used for the LCD background illumination, especially<br />
in older devices. Whilst only one or two lamps are generally used in notebooks,<br />
televisions are fitted with up to 82 tubes (FEM & IUTA 2011). The cold cathode tubes<br />
in a notebook have a diameter of approx. 1.5 mm and weigh less than 1 g (see Figure<br />
2).<br />
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